High-voltage transformer



1954 H. SCHNEIDER HIGH-VOLTAGE TRANSFORMER Filed Feb. 15, 1951 Fig.2

A.= Centre line of F 3 fhe LDlumn Symmetrical g UXIS 0f fhe shell fypetransformer Fig. 4

Patented Aug. 17, 1954 2,686,905 HIGH-VOLTAGE TRANSFORMER HansSchneider, Zurich, Switzerland, assignor to Ateliers lie Oerlikon,zerland Application February 15, 1951,

Construction Oerlikon, Zurich- Switzerland, a

corporation of Swit- Serial'No. 211,009

Claims priority, application Switzerland February 15,

4 Claims.

In high-voltage testing transformers with one pole grounded thehigh-voltage winding is frequently arranged in the shape of a so-calledlayer winding. Such winding consists of a large number of concentric,substantially cylindrical layers of helically wound coils of diminishinglength mounted on and surrounding the central leg of a shell type ironcore, a similarly shaped low-voltage helical winding being disposedbetween such leg and the inside of such highvoltage winding. The layerof the high-voltage winding nearest to the low-voltage winding leads tothe grounded pole of the transformer, the outermost layer to thehigh-voltage pole. As the voltage increases the layers are shortenedmore and more in the axial direction and the insulation spacings arethus increased toward the iron core. The practice has also been adoptedto design output transformers with layer windings so as to avoidvibrations surges.

In the drawing:

Figure 1 is a diagrammatic view of one-half of a transformer having alayer type winding; and

Figs. 2, 3, 4 and 5 are similar views of different modificationsillustrating the invention.

As shown in Fig. 1 a transformer is provided comprising an iron core Iof the shell type having a central leg on which is mounted a-low-voltagewinding 2. Such low-voltage winding is surrounded by a high-voltagewinding 3 which is compcsed of several layers: seven in the case of Fig.l. The intermost layer is grounded, the outermost is connected to thehigh-voltage line. The greater the number of layers that are intro ducedthe smaller becomes the potential difference between the individuallayers. This however makes the windings considerably more expensive andcomplicated. It is therefore advantageous not to increase the number oflayers too much. However, this endeavor is counteracted by the followingfact.

As the transformer output increases the additional losses in the windingmust be taken into consideration more and more, especially at a networkfrequency of 60 cycles. If in the case of large transformers one wishesto keep these additional losses within moderate bounds, the winding Wire(generally copper wire) must have only a comparatively small dimensionin the direction in the event of voltage ingly. The number of turnssmall and the large. In order to conceivable to give conductor correctthis evil it would be different dimensions to the in the various layers.The layers near low voltage winding and the stray flux iscorrespondingly increased, producing the well-known unfavorable effectsin the operation of the transformer.

According to the back is out increasing the stray flux. consists insubdividing the layer stray flux path or parallel strands and incrossing the latter by each other in such a way that their position asregards the stray field is equivalent.

As shown in Fig. 1, the innermost layer of the high-voltage winding 3nearest to the stray channel gives rise to inadmissibly high additionalwinding losses. To overcome this difliculty such layer is subdivided, asshown in Fig. 2, into two parallel strands 3a and The latter are crossedat the center, so that with respect to their position in the stray fieldthey are equivalent. In this manner it is possible to reduce largely theadditional losses in the innermost layer. Moreover even the windings ofthis layer may be increased in number, which leads to a reduction of theleakage. If necessary, additional layers, e. g. the second layer or thesecond and the third layer, may be subdivided in the same manner intotwo parallel strands.

it may be advisable to subdivide one layer into more than two parallelAn example or this is shown in Fig. 3. In such case the innermost layeris subdivided into three parallel spiral strands and the adjacent layerinto two.

In order to reduce in the event of surges the inner oscillations as muchas possible, the two extreme layers 4 and 5 which have few windings andconductors of small dimension may be arranged perpendicular to the strayflux. As shown in the example of Fig. 4, the subdivision into parallelspiral strands would then be efiected on the side of the stray channel,starting from the second layer only.

The oscillating capacity may be also reduced, as shown in Fig. 5, byarranging outside the outermost layer an electrostatic shield and byconnecting the latter to the beginning of the winding.

The manner and process of constructing the device of the invention areaccomplished by isolating the helically wound strands of the selectedlayers to be transposed at the zone or zones of transposition, and bycross-connecting such strands so that, for example, an inner strand andan outer strand form one conductor coil, while the adjacent outer strandand inner strand form another conductor coil, such strands beingconnected in parallel at opposite ends of the coils (helically woundlayers). As a result a reduction in the total number Of layers and areduction of additional losses are accomplished.

Having thus described my invention I claim:

1. A high-voltage transformer comprising a shell type core having acentral leg, a low-voltage helical winding surrounding such leg, asinglepole grounded high-voltage winding composed of a plurality ofannular individual layers of helically wound coils surrounding saidlowvoltage helical winding in concentric relation therewith and with oneanother, means connecting one terminal of said high-voltage winding toground at one end of the layer next adjacent said low-voltage winding,means connecting said layers in series circuit relation with oneanother, a selected inner layer of said highvoltage winding, which isotherwise subject to an objectionably high stray fiux path consisting ofat least two inner and outer helically wound strands, means electricallyconnecting said strands together in parallel only at opposite ends ofthe strands, and means cross-connecting the inner and outer strands inseries with one another between opposite ends of such strands wherebytheir positions with respect to such stray flux path thereof areequivalent, the remaining layers consisting of single solid conductors.

2. A high-voltage transformer as defined by claim 1, in which saidselected inner layer is the innermost layer of the high-voltage windingand consists of three helically wound concentric strands cross-connectedat three uniformly spaced points lengthwise of such layer, said threestrands being electrically connected in parallel only at the ends ofsaid strands and the next adjacent layer of said high-voltage windingaround said selected layer consists of two helically wound concentricstrands cross-connected midway of the length thereof and electricallyconnected in parallel at their opposite ends.

3. A high-voltage transformer as defined by claim 1, in which the axiallengths of the layers of the high-voltage winding disposed between theinnermost and the outermost layers thereof decrease in length one fromthe other.

4. A high-voltage transformer as defined by claim 1, in which meanscomprising an electrostatic shield is disposed outside the outermostlayer of the high-voltage winding, and means connecting said shield tothe other terminal of said high-voltage winding.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,872,247 Cole Aug. 16, 1932 FOREIGN PATENTS Number CountryDate 71,238 Norway Nov. 4, 1946 169,150 Switzerland Sept. 1, 1934340,227 Great Britain Dec. 18, 1930 500,775 Great Britain Feb. 15, 1939

